The REST and Database sections overlap in responsibilities, and the
Database subsections are getting quite long.
This clears up the responsibilities:
- Database operations belong primarily in `Database`
- Things that are specific to RESTful interactions (such as API keys)
belong primarily in `REST API`
- `REST API` has a hub page that links out to `Database` for database
operations
Left nav for the Database sectionis reorganized to make it more
beginner-friendly. `Fundamentals` and `Working with your database
(basics)` is what you really need to know to get started, and the rest
can be figured out later.